mackie 1604 vlz bad channel

[movek1]

can someone please point me in the right direction, ive had a few of these mixers and there has always been at least one channel thats out (no signal through that channel).
So where shoul i look first, caps, sensing resistors, ic, gain pot.
To be more clear channel 10 is out competely, channel 12 you can here when u turn up gain as if it were bleeding through, very faint.
the picture below is of the board

[Enzo]

First, pull the ribbon cables off and push them right back on. That cures most signal path interruption problems on those small Mackie mixers.

On any channel, probe the insert jack. Dirty contacts there will kill a signal just like a bad FX loop jack in a guitar amp. And just like an FX loop. check if the send part sends and if a signal into the return part makes it on through the mixer.

Of all the parts in each channel, after dirty insert jacks, the slider is by far the weakest link. You can hot the lever and pop the bottom out, they get dirty, they simply fail open. COmpare to a good channel next door. Does signal appear at the top end? (top end electrically - I don;t know which physical end is which) Power off, set the sliders at some mid point. Measure resistance between ends and to the slider from each end. Bad channel measure different?


Use the PFL, is signal present that far?

[movek1]

thanks enzo, the ribbons were the first thing i checked, these things are known for the ribbon cables going bad, or if your rushing, and its something ive done a few times, is install the cable 1 pin off, then you got LED's going on where they shouldnt be.
But anyway i swapped the fader, gain pot, and the 1/4 jack and still the same results.
Im just going to focus on channel 12 for now, for some reason, no signal when plugged in all the way, but there is signal when its half way in.Like i said, i already put a new 1/4 jack in and still the same result.
So input, fader and pots have been checked, what now.
Does anyone have a schematic of this mixer, (mackie cr 1604 vlz)
movekmusic@yahoo.com